Mixer



W. L. CUMMINGS MIXER April 10, 1962 Filed May 3, 1960 nite States PatentMIXER am C mm n B ekl ne Mas assigner a Wilevco, Inc., Newton Center,Mass, a corporation of Massachusetts Filed May 3, 1960, Ser. No. 26,494

Z'Claims. (Cl. 2594) This invention relates to mixing devices and moreparticularly to a novel device especially adapted for mixing a liquidwith a flowable material such as a powder, another liquid, or the like.I

Heretofore, in the art of mixing dry powders and solvent liquids, forexample, the uniform mixing with a fluid with many materials has'beerr aserious problem. With many powders to be mixed with a'liquid' such aswater, for example, the powder might require an appreciable time to bewet out or otherwise assimilated with the Water until it formed auniform mixture without lumps, or the like. Until such was accomplished,the powder not only tended to stick to itself to form lumps which didnot wet out readily, but also tended to stick to the walls of the mixingvessel and build up substantial deposits which tended to cause cloggingand other difficulties.

As a result, many complicated mixers have been devised to cope with thissituation, such as the well-known inter-rotating mechanically operatedheaters, and the like. However, though such devices certainly aid themixing process, they by no means solve the problem of build-up of stickydeposits. This is particularly so in the early stages of the mixingprocess before the powder or the like has been sufficiently wet out sothat it still is highly sticky.

Accordingly, it is an object of the present invention to overcome theseproblems of the prior art by the provision of an extraordinarilyeffective simple mixing device which is uniquely effective in the mixingof a potentially sticky powder or the like with a liquid. Furthermore,the unique results of the present invention have been accomplished byextraordinarily uncomplicated means, entirely free of conventionalbeaters or similar complicated and expensive mechanical devices.

More specifically, the unique and novel mixing device of the inventionutilizes for mixing the retroverted flow of a stream of liquid whichfirst flows upwardly generally uniformly throughout an annularcross-sectioned stream and then reverses itself to flow downwardlythrough the center of the annular stream. The powder or other materialto be mixed with the fluid stream is deposited at a desired rate by anysuitable means spaced upwardly from the fluid surface generallycentrally of the reversely flowing stream. The retroverted mixing streamcharacteristic of the invention may be created by uncompli catedstructures, such as, for example, a pair of vertically arrangedconcentric cylinders, the inner at its upper end terminating short ofthe outer. Suitable means such as a pump are provided for feeding theliquid to be mixed into the annular volume between the concentriccylinders and causing its upward flow therebetween so that it overflowsthe top of the inner cylinder and fiows radially inwardly and thendownwardly therethrough together with the powder or other material to bemixed therewith which is deposited at a predetermined rate generallycentrally of the inner cylinder. With such a structure, with the innercylinder entirely covered by a flowing stream of liquid, the powder tobe mixed never touches any wall of the mixing device until sufficienttime has elapsed for it to be wet out beyond the sticky state. Thepowder dispenser, being spaced above the liquid surface, is not affectedthereby to cause powder to stick to it. A suitable length for the innercylinder allows sufficient time for the wetting out of a given powder.

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Reference is now made to the following detailed descri'ptiori'of apreferred embodiment of the inven ti'on, to-

gether with the accompanying drawings','wherein:

FIG. 1 is'a vertical cross-section of the novel mixing device of theinvention, and

FIG. 2' is a cross-section of the mixing device of FIG. 1 taken on theline 22 thereof.

As will be apparent from the drawings, the novel mixing device of theinvention may consist of a'vertically arranged outer cylinder 12 and aconcentric inner cylinder 14 forming an annular volume 16therebetweenanda cylindricalvolurne 18 within the inner' cylinder. Thetop edge 20 of the inner cylinder terminates short of the top edge 22 ofthe outer cylinder. A radial b'ottomwall 24 connects the twocyliiidersatthe lower edge of the outer cylinder. A liquid inlet in theforr'n of apipe 26 is provided adjacent the bottom wall'24, and a pump 28 isconnected thereto for supplying liquid at a suitable predetermined rate.The inner cylinder 14 extends through the bottom wall 24 and is of anysuitable length for accomplishing the desired wetting-out of a specificpowder to be mixed with the liquid. The mixture may thereafter be pipedor otherwise directed to a reservoir, or the like (not shown).

For depositing the powder or the like at a predetermined rate generallycentrally of and preferably within the extent of inner cylinder 14,suitable means are provided positioned thereabove, well above the liquidsurface. For example, a hopper 30 having a distributor impeller 32rotatably mounted in the bottom opening thereof and driven by anysuitable means, not shown, may be used. Other devices, such as vibratoroperated means, or suitable orifices if another liquid is to be mixedwith that fed into the mixing device of the invention, may also be usedas appropriate.

In operation, as has been described hereabove, a retroverted flow ofliquid is provided by pump 28 or otherwise at a predetermined rateupwardly through the annular volume 16, to overfiow the top edge 20 ofinner cylinder 14 and then downwardly through the cylindrical volume ofinner cylinder 14. Because of the radially inward flow of the liquid fora substantial depth over edge 20, as at 20a, particles 34 of the powderor other material to be mixed with the liquid provided at apredetermined rate from hopper 30 upon the area adjacent the upper edgeof the inner cylinder, particularly if the powder particles tend tofloat, are carried away from both of the cylinders in a direction towardtheir common axis, as shown. Thus, sticky wet powder particles cannotreach and stick to any part of the mixing device of the invention, butrather are kept in the center of the downwardly flowing stream withininner cylinder 14 until they have suflicient opportunity to bethoroughly wet out and uniformly mixed with the liquid free of lumps, orthe like, to provide a mixture of predetermined ratio.

It will be apparent to those skilled in this art that there may existvarious modifications thereof within the spirit of the invention and thescope of the appended claims.

I claim:

1. A liquid mixer comprising a vertically arranged outer tubular memberand an inner tubular member having walls spaced inwardly from said outertubular member and having its upper edge terminating short of the upperedge of said outer tubular member with a lower wall portion connectingsaid inner and outer tubular members, means for establishing aretroverted liquid stream having an upwardly flowing portion of annularsection through the annular volume between said inner and outer membersand a downwardly flowing portion of tubular section within said innermember, with said portions connected by a radially inwardly flowingportion passing over the periphery of the upper edge of said innermember and defining an annular liquid surface within said outer tubularmember, including means for feeding liquid into the volume between saidinner and outer members and means for removing liquid from the lower endof said inner tubular member below said lower wall, and means spacedabove said inner member upper edge and said liquid surface fordepositing a material to be mixed with said liquid upon the areaadjacent the upper edge of said inner tubular member.

2. A liquid mixer comprising a vertically arranged outer tubular member,an inner tubular member, said inner tubular member being substantiallycoextensive with and positioned within said outer tubular member, saidinner tubular member having walls spaced inwardly from said outertubular member and having its upper edge terminating short of the upperedge of said outer tubular member, a wall connecting said inner andouter tubular members, means for establishing a retroverted liquidstream having an upwardly flowing portion between walls of said innerand outer members and a downwardly flowing portion of tubular sectionwithin said inner member, with said portions connected by an inwardlyflowing portion passing over a major portion of the periphery of theupper edge of said inner member and defining a liquid surface Withinsaid outer tubular member, including means for feeding liquid into thevolume between said inner and outer members and means for removingliquid from the lower end of said inner tubular member, and means spacedabove said inner member upper edge and said liquid surface fordepositing a material to be mixed with said liquid upon the areaadjacent the upper edge of said inner tubular member.

References Cited in the file of this patent UNITED STATES PATENTSRevallier Nov. 22, 1955 Caldwell et a1. May 5, 1959

